Earth drains

ABSTRACT

An earth drain comprising a core consisting of an elongated flexible web having on at least one surface thereof, and preferably on both surfaces, an array of discreet projections spaced transversely across the width of the web, and longitudinally in the lengthwise orientation of the web. The array of projections is interrupted by a plurality of elongated projection-free zones extending in the longitudinal direction of the web, and spaced transversely across the width of the web. A filter of sheet-like water permeable material encases the core, and is adapted to be maintained in spaced relationship to the web by the free ends of the projections thereon.

This application is a national stage application of internationalapplication number PCT/CA94/00281 filed May 18, 1994, now abandoned.

The present invention relates to earth drains for the drainage of soilhaving low water permeability such, for example, as clay.

More specifically, the type of earth drain to which this inventionrelates consists of a core comprising a relatively flat, flexible,elongated web having surface projections, usually on both sides thereof,which core is encased in a filter of water permeable sheet-likematerial. The projections on the web surfaces of the core serve tomaintain the filter in spaced relationship with the web. Such drains areusually driven vertically into the ground to a substantial depth. Inuse, water passes through the free surface area of the filter i.e., thatarea of the filter which is not in contact with the web projections, anddrains away through the space between the web surface and the encasingfilter material. Drains of this type are illustrated in Oleg WagerCanadian patent No. 930,999 dated Jul. 31, 1973, and Oleg Wager Canadianpatent No. 1,015,173 dated Aug. 9, 1977.

The drain described in Canadian patent No. 1,015,173 constituted animprovement of the drain described in the earlier Canadian patent No.930,999. The drain disclosed herein constitutes an improvement on thedrain described in Canadian patent No. 1,015,173, in that the drain ofthe present invention can be produced much more economically as a resultof substantial savings in raw material costs and improved productionefficiency while maintaining the satisfactory performance of the earlierdrain.

In a broad aspect, the earth drain according to the present inventioncomprises a core consisting of an elongated flexible web having on atleast one surface thereof, and preferably on both surfaces, an array ofdiscreet projections spaced transversely across the width of the web,and longitudinally in the lengthwise orientation of the web. The arrayof projections is interrupted by a plurality of elongated projectionfree zones extending in the longitudinal direction of the web, andspaced transversely across the width of the web. A filter of sheet-likewater permeable material encases the core, and is adapted to bemaintained in spaced relationship to the web by the free ends of theprojections thereon.

The web is typically of uniform width and indeterminate length, and theprojections are preferably of uniform length or height (as measured fromthe surface of the web) and of uniform shape. Typically, the projectionswill be of frusto-conical shape. However, the projections can be ofcylindrical configuration or may have a circular, square, hexagonal, orother cross-section.

Preferably, the projection free zones will have a transverse width equalto or greater than twice the transverse spacing of adjacent longitudinalrows of projections. The projection free zone will be separated by atleast two longitudinal rows of projections. Projections in adjacentrows, when viewed in either the longitudinal or transverse direction ofthe web will preferably be staggered by one half the spacing betweenadjacent projections to reduce the distance between unsupported areas ofthe filter in the projection covered areas of the web.

While the elongated projection free zones of the web may extendthroughout the length of the web, preferably such zones will beinterrupted at regular intervals in the longitudinal direction of theweb by bands of transverse rows of projections which extend, with orwithout interruption, completely across the width of the web. Thepurpose of these transverse bands is to provide for a cross-flow ofwater flowing through the drain in the event of transverse blockage ofthe drain in those projection free zones in which the filter isunsupported by the tops of project ions.

The elongated projection free zones may be longitudinally alignedthroughout the length of the web. Alternatively, the transverse spacingof the elongated projection free zones on opposite sides of eachtransverse band of projections may be staggered so that a projectionfree zone on one side of the band will be longitudinally opposite anarray of projections on the opposite side of the band.

In drawings, which illustrate embodiments of the invention:

FIG. 1 is a schematic plan view, partially broken away, of an endsegment of an embodiment of the drain according to the invention;

FIG. 2 is a schematic plan view similar to FIG. 1 of a second embodimentof a drain in accordance with the invention;

FIG. 3 is a plan view, partially broken away, on an enlarged scale ofthe drain of FIG. 1;

FIG. 4 is a fragmentary cross-section of the drain depicted in FIG. 3through the line IV--IV, but including the filter; and

FIG. 5 is a schematic side elevation of a distorted drain in actual use.

Referring now to FIGS. 1 and 2, the drain illustrated generally at 10comprises a core 11 which consists of a generally flat, flexible web 12and an array of discreet projections 13. As will appear from FIG. 4, theprojections are disposed on both sides of the web 12, and the completecore is encased in a sheet-like filter 15 which is supported in spacedrelationship to the web by the free ends of the projections 13. Thefilter is composed of a suitable water permeable material, whereas thecore and projections are composed of water impermeable material.Accordingly, when the drain is inserted in the soil, water may passthrough the filter (which prevents the ingress of soil particles) intothe space between the filter and the web so that water may flow throughthe drain in the space between the filter and the web.

It will be seen that the projections 13 are regularly spaced in both thetransverse and longitudinal directions of the web to form transverse andlongitudinal rows. Adjacent rows, when viewed in either the transverseor longitudinal direction are staggered with respect to each other in asense that the projections in one row are displaced one half thedistance between the projections in the adjacent row in order tominimize the unsupported area of the filter in the projection coveredareas of the web.

According to the present invention, the array of projections 13 on theweb is interrupted by a plurality of elongated projection free zones 14extending in the longitudinal direction of the web, and spacedtransversely across the web. These projection free zones permit freeuninterrupted flow of water along the drain under normal operatingconditions and, of course, the provision of the projection free zonesgreatly reduces the number of projections on the web, and, consequently,greatly reduces the cost of raw materials required to form the core, andthe weight of a unit length of the drain.

The projection free zones typically will be equivalent in width to twoor three times the transverse spacing of adjacent longitudinal rows ofprojections. The length of the projection free zones is not particularlycritical. Indeed, the projection free zones can extend for the entirelength of the web, although, typically, they will be interrupted bytransverse bands 20 of projections which extend completely across thewidth of the web to interrupt the elongated projection free zones atregular intervals along the length of the web. In a typical drain thiswill result in a plurality of elongated projection free zones inalignment throughout the length of the drain and spaced transverselyacross the drain. However, as illustrated in FIG. 2, the elongatedprojection free zones on either side of a transverse band of projections20 may be staggered or displaced laterally one half the transversedistance between laterally adjacent projection free zones 14 to resultin a staggered arrangement along the length of the drain. It is alsopossible that the bands 20 will be discontinuous in the sense that theywill interrupt the projection free zones across the web at differentlongitudinal locations, while still providing for cross-flow over theentire width of the web.

A segment of a typical drain is illustrated in greater detail in FIGS. 3and 4. Referring particularly to FIG. 4, it will be seen that theprojections are frusto-conical in shape, with the larger base adjoiningthe web 12, and the smaller free end supporting the filter 15. Further,it will be seen that the web is provided with a number of apertures 30extending therethrough which permit the passage of water from one sideof the web to the other. This, in conjunction with the transverse bandsof projections 20, which provide cross-flow zones at regularlongitudinal intervals along the web facilitates the unimpeded flow ofwater through the drain even in the event of local blockage.

Local blockage may occur, particularly in the projection free zones, asa result of lateral soil pressures which force the filter inwardly intocontact with the web. Such deformation of the web is illustratedschematically by dotted lines 35 in FIG. 4 when such deformation occurs,the passage of water along the drain in the area of the local blockagewill be impeded. However, a relatively free flow of water and steadyvolume of water flow along the drain is assured because the water, inthe area of the blockage, may circumvent the blockage by flowinglaterally into the adjoining projection covered zones, and thereafter inthe longitudinal direction of the drain. Additionally, water above theblockage may flow through apertures 30 from one surface of the drain tothe other, as it is highly unlikely that both surfaces would be blockedin the same area and on opposite sides of the drain. However, even ifthis should occur, the projection covered zones of the web on eitherside of each projection free zone assures both lateral and longitudinalflow of water.

Similarly, as a result of unstable soil conditions, earth drains of thetype to which this invention relates are subject to deformation which isillustrated in FIG. 5. As a result of the subterranean shifting of soilfor various reasons, drains which were originally substantially straightwhen installed, may be subject to severe deformations (micro folding)which, in some known drain designs would result in complete blockage ofwater flow in the longitudinal direction of the drain. However, as aresult of the longitudinally continuous array of projections and thebands 20, providing cross-flow zones, the drain of the subject inventionwill remain unblocked even under severe micro folding such as thatdepicted in FIG. 5. In other words, the projections will always maintaina spacing between the filter and the web to permit the flow of waterthere along, and the cross-flow zones 20 will always permitredistribution of flow transversely across the drain in the event ofblockage in certain local zones, such as the projection free zones.

Typically the projection free zones will be spaced apart by at least twolongitudinal rows of projections, although a somewhat greater spacingmay be desirable. The exact spacing, as well as the longitudinal spacingof the cross-flow bands 20 may be selected depending upon the drainagerequirements, the nature of the soil being drained.

Similarly, the length of the projections may vary depending upon thedrainage requirements, and the spacing of the projections may also bevaried depending upon the nature of the filter material being used, andother conditions such as those Just mentioned. The standard core widthof drains of this type is 100 mm, and, by way of example the length ofthe projection may be 1.25 mm.

While a particular embodiment of the drain has been illustrated by wayof example, it will be appreciated that many modifications are possiblewithout departing from the scope of the invention. For example, whilefrusto-conical shaped projections have been illustrated, the projectionscould be cylindrical and/or of cross-section other than circular, forexample, square, hexagonal, oval, or the like. While it is obviouslypreferable to have all projections in a single drain of uniform shapeand height, there is no reason why different shapes and heights couldnot be utilized, for example, in adjacent longitudinal 0F transverserows. Further, as noted previously, the particular spacing and height ofthe projections, the number and width of the projection free zones, andthe width of the projection covered zones between the projection freezones may be varied depending upon the specific conditions and drainagerequirements in a particular area.

Compared with the known drain described in Canadian patent No.1,015,173, the costs of manufacturing the drain of the subjectapplication are appreciably less. The provision of the projection freezones constitutes a considerable reduction in raw material costs and thereduced net volume of projections results in a shallower draw for theplastic resin during the core forming process. This will relax rawmaterial specifications, as the drain will be easier to manufacture,thus permitting a much wider selection of resins from which to choose,including reprocessed or recycled materials which, again, will result ina significant reduction in raw material costs and benefits-to theenvironment.

We claim:
 1. An earth drain comprising a core consisting of an elongatedflexible web having on at least one surface thereof an array of spacedprojections, each having a base end affixed to said web, and a free endspaced from said web, the projections of said array being evenly spacedin parallel rows extending longitudinally and transversely of said weband a filter of sheet-like water permeable material encasing said atleast one surface and adapted to be maintained in spaced relationship tosaid web by the free ends of said projections, characterized in thatsaid array of projections is interrupted by a plurality of transverselyspaced elongated projection free zones extending longitudinally of saidweb, the dimensions of said projection free zones in the transverse andlongitudinal directions of the web being greater than the spacingbetween adjacent projections.
 2. An earth drain as defined in claim 1,wherein said web is of uniform width, and array of projections isdisposed on each surface thereof and said filter encases said core. 3.An earth drain as defined in claim 2, wherein said projection free zonesextend the length of said core.
 4. An earth drain as defined in claim 3,wherein said projection free zones are spaced at regular intervalstransversely of said web, and adjacent projection free zones are spacedapart by at least two longitudinally extending rows of projections. 5.An earth drain as defined in claim 2, wherein said projection free zonesare spaced at regular intervals transversely of said web and arelongitudinally interrupted by transverse bands comprising at least onetransversely extending row of projections.
 6. An earth drain as claimedin claim 5, wherein said transverse bands extend without interruptionacross the width of the web.
 7. An earth drain as defined in claim 6,wherein said transverse bands comprise at least two transverselyextending rows of projections.
 8. An earth drain as defined in claim 6,wherein the elongated projection free zones on one side of each band arelaterally displaced one half the distance of the transverse spacingbetween the elongated projection free zones on the other side of theband to produce a staggered arrangement of said projection free zonesthroughout the length of the web.
 9. An earth drain as defined in any ofclaims 1, 2, 3, 4, 5, 7, 8 or 6, wherein the projections in adjacentlongitudinally and transversely extending rows are displaced a distanceequal to one half the spacing between adjacent projections in a row,whereby rows of said projections in the longitudinal and transversedirections are staggered with respect to adjacent rows.
 10. An earthdrain as defined in claim 9, wherein the width of said projection freezones is equal to three times the transverse spacing of adjacentlongitudinal rows of projections.
 11. An earth drain as defined inclaims 1, 2, 3, 4, 5, 7, 8 or 6 wherein said projections are offrusto-conical configuration.